My manager, Judy Hofflund—she's been my manager for 15, 16 years—sent a message about three years ago saying, ‘Would you ever be interested in directing a film of Thor?' I said yes. It was intriguing. I knew the comic and I knew a bit about the Norse myth and there began two or three months of conversation with Marvel. I was just one of a number of people they had been speaking to. They'd been developing it for about five years and we tried to figure out if we were to proceed, whether we would end up making the same picture. That process across those two, three months, I found exciting. I got to know the material again and became a little more aware of how Marvel Comics had presented the character and realized what an incredible opportunity—challenge—it would be to try and produce this great, big would-be popular entertainment. And all the acquisition of knowledge about visual effects and digital worlds that would be relatively new to me. I thought that would be a fantastic combination, so we kept talking and eventually they offered me the job.

Unlike every other Marvel hero, we have a day of the week named after Thor. What informed you when you were conceiving your direction for the film and did you look outside what was in the comic pages?

Oh, definitely. The two things that I was reading side by side from the moment we all became involved were the comics and the Norse myths themselves. I started with the Penguin Book of Norse Myths, a small, slim volume where the myths are presented fable-style so each of them is a page, page and a half, maybe two or three pages at the most, which tell you how Odin lost his eye or how Loki was able to perform certain tricks—three other days of the week also come from Norse mythology [Tuesday, Wednesday and Friday]. From there, it was possible from the myths and the comics themselves to see this little saga where across the whole thing you have a root of strength and sensitivity in the hero, you have prehistory and space travel, you have dynastic sagas, you have memorable villains, you have complex psychology so you have color and drama and depth and foundation—all of these. It's a very, very rich mix. Of course, as soon as all of those things are at play, the big issue becomes, what's the tone of the film, how do you make it cohere-essentially, that's a question Marvel asked me on Day One and they're still asking me. We know that we're trying to deliver that plus everything else: the adventure, the spectacle, the emotion and the action. But it's a summer movie—we're kicking off a summer and you want to go and give people a good time and for everything else to be lightly worn. That was the attraction: all of those combinations and how you make them work together.

I was surprised at how funny the film was. In Vegas at CinemaCon, the coffee cup scene got a huge laugh.

There's comic tension inherent in this very entitled fellow, very well played by Chris Hemsworth. He has a very good touch with the light comedy. The funny thing about him is he's physically impressive and can absolutely hold his own in the action stuff, but he's also just as winning in the light comedy scenes, the romantic scenes. That's where, again, when Marvel would say, "How are we going to do this? How are we going to have this sense of fun? How are we going this united tone?" we all agreed it started with casting. It starting with casting that provided actors that were complex and had a range of gifts, and it absolutely started with Thor.

I heard that Hemsworth put on so much muscle he outgrew his own costume.

Alex Byrne, Oscar-winning costume designer, rang me in distress the evening of the day in which we'd shown some costume tests. We were about three weeks away from shooting and she said, "You know that incredibly sculpted suit, that kind of curves around every muscle of his? None of the sculpting is there anymore, it's just been blown out by his new inches—even the size of his neck is a massive jump from just two or three weeks ago." I had to make a call to Chris saying, "Please, please, please calm down." He said, "Thank God because it would be nice to get to a point when I actually enjoy eating food again." In rehearsals, I'd be in the middle of giving him a note and he'd go, "Sorry Ken. Gotta stop now," and in would come somebody with what seemed like half a chicken! He has to eat it. He'd say, "If I don't eat it, I'm either going to collapse or you're going to lose all these muscles." That was kind of a comic dimension to it all. It was like feeding a steam engine. Then he'd leave my room and go down and do all the stunt work for a bit. They literally had to have people coming every two hours to give him enormous amounts of protein.

He must have felt like a Viking king if people were just always coming by and serving him food.

Exactly. It was like you were at the court of Henry VIII or something. You could have drawn a picture of our rehearsal room and it would look like a banqueting scene from the comics.

While we're talking about casting, were you surprised by the controversial reaction to casting Idris Elba, or were you steeled for it?

I suppose I was surprised. I respect the passionate feeling about this work. It's pretty exciting that people care about the picture and that there's a great degree of interest and anticipation—which frankly is a privilege and sort of rather rare and thrilling—but I was surprised. My attitude is to be pretty open. For instance, in the Shakespeare films I've cast color-blind, ethnicity-blind. For me, a classical approach need not be sort of documentary-like. But my experience comes from doing Shakespeare, where my attitude is that nobody really knows anything and that we have a very shady view of what's authentic. Anyway, I believe there is a degree of license available at the very least and beyond that my simple gut was telling me that for all the characteristics that Heimdall possesses, Idris Elba was a magnificent choice and I don't think the color of his skin contradicts anything in the story or throws or confuses anything. It's a personal point of view, but it's one in which I have complete conviction.

He's so talented.

Oh yeah. It's going to be one of those things where when you see him in the part, it will be an absolutely redundant issue. People will not be talking about it once they see him in the role and see the approach to the piece. It's a choice but I think it's a valid choice. I think it's the right choice.

Do you think this Thor film tells Thor's full story or do you feel like it's open for sequels?

I never really kept an eye on sequels. I think anytime you kind of start planning for the things that may happen, it's a little dangerous. The picture has to do the talking from this point; the audience will decide whether they're remotely interested in seeing more of these stories. I know they'll be interested in seeing The Avengers because it's such an unusual combination of characters and stories and themes. Ask me in about six weeks. Listen, there are hundreds and hundreds, probably thousands, of myths inside the Norse canon—and there's certainly 50 years of Marvel Comics. There's plenty of material to choose from. The end of this particular movie, we chose, I hope, a genuinely interesting way to leave some questions unanswered. I love leaving a film with a few things to talk about that are not all wrapped up in a nice big bow, and if people feel the same way then there will be places to go.

Technically, this isn't your first action film—your Henry V had tons of sword-swinging and fighting. Was anything from that experience or your stage work that you were able to use here?

I think a very, very key and memorable moment in my film career was one morning at 27 years of age. It was 8:00 a.m. on a cold and frosty November morning in a field in Southern England standing next to a camera and a first assistant saying to me, "So Governor, it's the Battle of Ashencourt—where would you like to start?" It had me going, "Christ, obviously it's supposed to be 27,000 French and 3,000 English. How many have we got?" "We've got 42, sir." "And hundreds and hundreds of horses, how many have we got?" "We've got 17, sir. 17 horses, 42 people but there's a lot of smoke and a lot of rain." "That's great. Okay let's put them a very long way away." What it did teach me, I suppose, was just to be imaginative with the way you invent action. One of the techniques we used was to try and get inside the center of the battle by literally being in the middle with a camera or using long lenses in order to squash up the background view. You become familiar with the rehearsal, the preparation, the planning and the little bit of give that makes an action scene a little different. I guess I was familiar with that enough to know about that balance between being prepared and being sort of spontaneous. I was certainly aware of how important it was for the actors to really know these routines inside out. We did rehearse a lot, and we rehearsed the fights a lot. We rehearse action stuff as much as we rehearse the dialogue scenes, which we also rehearsed a lot. I guess what I learned was you couldn't prepare too much because it was always going to be different on the day and take on a life of its own—but it still needs a solid bedrock of preparation.

You must also have had to focus a lot of attention on the way Thor speaks, taking the grandiose language—which of course, you've directed plenty in your Shakespeares—but with the added challenge of blending that dialect into the modern world.

I suppose I said to everybody that I wanted fearless acting. Just have it be real, have it be truthful, have it be actually naturalistic. People like Chris as Thor, people like Tony Hopkins as Odin, needed to be unafraid of the size that sometimes is required when your job is to rule the galaxy. There's this sort of paradox: we enjoy finding humanity in the gods, seeing godlike qualities in humans, and it's nice when the two conflict. One of the things that I have always taught in Shakespeare is that accents are less important to me than the actual sound of the voice and the character making an invisible join. The main thing is that the truth of what they're saying is paramount, so we try to stop anybody doing any external or superficial grandness of tone. Nobody trying to speak louder or more formally than they need to. You're in the room, you're next to them speaking to them exactly the same way as you would if this was life. Don't suddenly start talking as though you're on a stage. Especially when you wear these kinds of costumes, the more naturalistic you can be, the more simple, the better the marriage. We mustn't try and compete our voices or in accents or in our delivery with the sets or the weapons or the colors or space. So, simplicity, truth—these are the things you are constantly using rehearsals to try and establish. A lot of times, especially what I'm describing, is just making sure that we as filmmakers and as actors got out of the way and let these characters do the talking in a sincere a manner as possible.

Now that you've shot in 3D, are there any of your old films that you wish you could go back and have done in 3D?

Henry V, I think. Action things. Henry V would be interesting in 3D; Frankenstein would be interesting in 3D. Aside from the action pieces and all the things you might expect could be enhanced or immersive in a different way in 3D, I'm actually finding that some of the more intimate character scenes in Thor are also benefiting from the sense of putting the audience as a genuine participant in scenes—that it's fun to be that close inside, particularly in the scenes between Natalie Portman and Chris Hemsworth. You're more of a different kind of participant in romantic scenes or funny scenes, so I suppose that mean that it's a pretty responsive format if you find the story—led way to use it. It can't always just be about things coming out and smacking you in the face. Sometimes it's got to do with just placing you inside the world of the film in a way that is even more engrossing, even more of an escape, and I think that can apply to quite a lot of movies.

You're playing Sir Laurence Olivier in the upcoming My Week with Marilyn. Being an actor, playing the greatest actor that has ever lived, according to many people, is that intimidating?

You certainly don't go into it too much in your mind. The first thing in terms of this project is that the script is excellent. As soon as you realize that this is a very tender, very funny, very surprising love story about the fun and madness of the creative process and it's from the viewpoint of this outsider who gets to be on the inside just for a moment, just long enough to fall in love, you realize that it's less about the greatest actor who ever lived but another participant in the process who was at a very interesting point in his career—as was Marilyn Monroe, who arrived in England to perform this picture, The Prince and the Showgirl, when she was essentially the biggest movie star in the world. When she arrived at the Heathrow Airport in London, she brought the place to a standstill. Her fame was absolutely global and intense. She couldn't go anywhere without stopping streets and stopping traffic. Basically it devolves down to two enormously talented people who have different views about how something should be done, and the script is very respectful, very affectionate, very funny, very illuminating about the pair of them. It celebrates their talents, but it doesn't hold back on how difficult, challenging and sometimes pretty dramatic it is when two very talented people come together and sparks collide. It was really that atmosphere observed by this young man who eventually falls in love with Marilyn that drew me to it and then I wanted to see the movie. I'm keen to see the movie—if I was a movie-goer, it would be on my list. Then the idea of playing Olivier was clear because on the page, he's a very complex and complicated human being. He isn't just the intimidating legend of the Greatest Actor Who Ever Lived-he's a living, breathing human being. And so in the end, the biggest concern was being able to be right up to par with the great Michelle Williams, who is a revelation as Marilyn Monroe—and it was one of the great pleasures of the film, as well. She is a tippity-top actress who is really going to surprise and delight people with this performance.